只能输入数字和字母

#define kAlphaNum   @"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789"

-(BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string{
  
    NSString *new_text_str = [textField.text stringByReplacingCharactersInRange:range withString:string];//变化后的字符串
    
    if (textField == self.borrowMoneyView.vinTextField) {
        
        //只能输入数字和字符
        NSCharacterSet *cs;
        cs = [[NSCharacterSet characterSetWithCharactersInString:kAlphaNum] invertedSet];
        NSString *filtered = [[string componentsSeparatedByCharactersInSet:cs] componentsJoinedByString:@""]; //按cs分离出数组,数组按@""分离出字符串
        BOOL canChange = [string isEqualToString:filtered];
        
        return canChange;
    }

return YES;